The present invention relates to a device for generating very high sound pressure in air for example to prevent trespass, intrusion or unauthorized staying in an area indoors or outdoors so as to deliver a warning signal calling for attention as a siren.
There are several devices based on different techniques which however have disadvantages as,
areas with lower sound pressure PA1 low sound pressure at frequencies important for public address PA1 low efficiency PA1 becomes very large and heavy when very powerful sound pressure is to be achieved